1. Field of the Invention
This invention relates to a brushless motor, a typical example of which is a spindle motor for a video tape recorder (VTR), and more particularly to a coil terminal extending structure of extending the terminals of a coil from the front surface of a wiring board to the rear surface.
2. Related Art
In a brushless motor, the rotary position of the rotor is detected with a magnetic sensor, and according to the result of detection, a motor driving IC on the wiring board controls the supply of current to the drive coil. In general, on the front surface of the wiring board, a stator on which a plurality of phases of drive coils are wound is mounted, and the end portions of those drive coils are drawn out from the front surface of the wiring board to the rear surface, and connected to wiring patterns formed thereon. Therefore, heretofore, the terminal parts are disposed in a core holder holding the stator core, and the end portion of the coil are connected to the front side ends of the terminal parts, and the rear side ends of the terminal parts are wired to the wringing patterns.
Sometimes, without use of terminal parts, the end portion of the coils are directly connected to the wiring patterns. In this case, holes are formed in the wiring board, and the coil terminal parts are inserted in the holes thus formed, so that the coils are drawn out from the front surface of the wiring board to the rear surfaces. In another method, no such holes are formed in the wiring board, and after being laid outside of the printed circuit board, the coils are drawn out from the front surface of the wiring board to the rear surface.
In the case where, as was described above, the coils are connected to the wiring patterns through the terminal parts, the number of components is increased as much as the number of the terminal parts, and accordingly the resultant brushless motor is increased in manufacturing cost as much. Furthermore, in the case of use of the terminal parts, it is necessary to wire the end portions of the coil and lead wires to both ends of each of the terminal parts. Therefore, the manufacture of the brushless motor is low in work efficiency and in productivity.
In the case where holes are formed in the wiring board, and the end portions of the coil are inserted into the holes thus formed, the manufacturing cost is increased as much as the holes are formed in the printed circuit board; that is, the resultant brushless motor is increased in manufacturing cost as much.
On the other hand, in the case where the coils are laid outside the wiring board, the coils come outside the wiring board. Hence, the parts of the coils which come outside the wiring board may touch other components such as a rotor, thus being broken. That is, the brushless motor is low in reliability.